I completely agree with this. To add onto your comment, as a teenager and with their "relationship" (platonic or romantic) she can only do so much. They already had a very little time to hang out with one another and now that she's making friends that time is even shorter. Spending time with her and going to the art studio were the only time's Hamin could be himself and have an outlet for his emotions (and now one of those things is gone
Also, not establishing a relationship is -in my opinion- worse than having an established one because it makes a person think "what could have happened if I just ---". So, it's understandable to me that she has a hard time moving on
Sorry for the mini rant

I feel bad for the girl. I think the reason why she can't focus on just Hamin is because that Gaeul or something has also a problem so she supports also her. And Hamin was so pressured because of his family (kinda feel the same way with him)